This invention relates to an automatic sewing machine and more particularly, to an automatic sewing machine for continuously sewing the edges of a work or workpiece having a plurality of edges contiguous to each other in angular relationship in succession.
In continuously sewing a work having a plurality of contiguous edges connected together in angular relationship to each other, such as a pair of trousers, after a first edge of the work has been sewn, in order to sew a second edge of the work, it is necessary to turn the work about the position of the sewing needle so as to align the second edge with the advancing or feed direction of the work.
One of the conventional methods for turning the work in the manner mentioned hereinabove has been illustrated in U.S. Pat. No. 3,425,369, for example. According to the prior art turning method, after a first edge of the work has been sewn, a vertically movable turning member is lowered down onto a portion of the work which hangs from the table to hold the work against the surface of the table, the turning member is turned with the work portion held against the table surface, and the work is turned about the position of the sewing needle on the table until a second edge of the work contiguous to the first edge thereof is detected by a detection means which is adapted to detect whether or not the second edge is aligned with the sewing or work advancing direction. However, in the conventional work turning method, since the turning member is designed to turn the work by a predetermined angle while holding the work in a predetermined position or constant distance from each of the work edges, there is the disadvantage that the turning member can not positively engage the work portion inwardly of a second edge of the work when the member turns to the work after a first edge of the work has been sewn. That is, generally, since a plurality of contiguous edges of a work are not in constant angular relationship or have varying angular relationship to each other, the turning member tends to engage the work in a position excessively inwardly of a particular edge of the work and in a position excessively outwardly of another edge of the same work, that is, it can not be assured that the turning member always engages the work in a predetermined constant distance from all the edges of the work. When the turning member engages the work in a position excessively inwardly of an edge of the work, the edge is caused to crease and thus, even if the creased edge can be aligned with the work sewing or feed direction, a satisfactory or proper sewing operation can not be performed at such an edge. On the other hand, when the turning member engages the work in a position excessively outwardly of a edge of the work with the contact face of the turning member maintained nonparallel to the surface of the table, the turning member can not positively hold the work edge and tends to desengage from the work while the work is being turned whereby the work edge can not be brought to the correct alignment with the work sewing or feed direction. In order to eliminate such disadvantages, it has been proposed to construct the turning member so as to have a sufficiently large size and cause its contact face to maintain a parallel relationship to the surface of the table. But even with such a turning member, there are still the disadvantages that a crease or creases develop in the edge of the work and the edge can not be positively held down.
Furthermore, in the prior art method mentioned hereinabove, in the waiting position of the turning member, if the turning member is positioned in a position insufficiently spaced from the table surface during a sewing cycle, the turning member is contacted by a crease or creases developed in the work edge, thereby impeding the sewing operation. And when the turning member is again moved to the work holding-down position positioned in a position insufficiently spaced from the table surface for the next work turning operation after one work turning operation, the turning member comes into contact with the crease or creases in the work edge to the degree that the sewing result will become unsatisfactory. For this reason, it is necessary that the turning member has to be positioned at an otherwise unnecessarily great distance from the table surface. This appreciably prolongs the time required for the work holding-down operation by the turning member and renders the construction of the turning member complicated.